Growth of kidney and anti-kidney vortices over a square jet in crossflow

Abstract

The present paper reports on triple-decked evolution of the kidney vortices and the growth of unsteady antikidney-type vortices over a square jet in crossflow. Incompressible direct numerical simulations are performed with Reynolds number 2000 and jet to crossflow velocity ratio 2.5, to extract such flow details. Out of the three different decks, the lower deck kidney vortices maintain their steady appearance over the jet hole; however, vortices in the middle and the upper decks were unsteady in nature. Frequent shedding of the frontal hovering vortices and their convex wrapping over the front part of the jet hole are found to be responsible for the multidecked growth of the kidney vortices. On the other hand, unsteady antikidney-type vortices are noted to grow over the central part of the hole, and their growth is verified to be attributed due to concave windward folding of the frontal jet shear layer. Notably, the present findings remained consistent with existing experimentally observed features of such flows.